The Americans with Disabilities Act (ADA) requires the removal of physical obstacles to those who are physically challenged. The stated objective of this legislation has increased public awareness and concern over the requirements of the physically challenged. Consequently, there has been more emphasis on providing systems that enable physically challenged people to access a motor vehicle, such as a bus or minivan.
A common manner of providing the physically challenged with access to motor vehicles is a ramp. Various ramp operating systems for motor vehicles are known in the art. Some slide out from underneath the floor of the vehicle and tilt down. Others are stowed in a vertical position and pivot about a hinge, while still others are supported by booms and cable assemblies. The present invention is generally directed to a “fold out” type of ramp. Such a ramp is normally stowed in a horizontal position within a recess in the vehicle floor, and is pivoted upward and outward to a downward-sloping extended position. In the extended position, the ramp is adjustable to varying curb heights.
Fold out ramps on vehicles confront a variety of technical problems. Longer ramps are desirable because the resulting slope is more gradual and more accessible by wheelchair-bound passengers. Longer ramps are, however, heavier and require more torque about the pivot axis to be reciprocated between deployed and stowed positions. To satisfy the increased torque requirement, some fold out ramps use large electric motors, pneumatic devices, or hydraulic actuators to deploy and stow the ramp. Often, these systems cannot be moved manually in the event of failure of the power source, unless the drive mechanism is first disengaged. Some existing fold out ramps can be deployed or stowed manually, but they are difficult to operate because one must first overcome the resistance of the drive mechanism. Further, fold out ramps require a depression (or pocket) in the vehicle's vestibule floor in which to store the retracted/stowed ramp. When the ramp is deployed, the aforementioned depression presents an obstacle for wheelchair passengers as they transition from the ramp to the vestibule, and into the vehicle.
Another technical issue confronting fold out ramps is the variety of situations in which the ramps must operate. Depending on the use of the vehicle in which a particular ramp is installed as well as where the vehicle is operated, the ramp might be deployed to curbs of varying heights, as well as to a road surface. In addition, the inclusion of a “kneeling” feature on the vehicle can affect the height of the vehicle floor relative to the alighting surface.
The deployment requirements of fold out ramps are also affected by road crown. In order to facilitate drainage, road surfaces are often sloped away from the center of the road. When a vehicle is parked on such roads, this “road crown” causes the vehicle to be tilted at an angle relative to a horizontal plane. For example, when a vehicle is stopped and positioned parallel to a curb, the vehicle is generally tilted toward the curb about a longitudinal axis. Because this tilt affects the structure to which the ramps are attached, the road crown affects the position of the deployed ramp relative to a horizontal plane.
As previously noted, a more gradual ramp slope is preferable because it makes it easier for wheelchair-bound passengers to enter and exit the vehicle. Although fold out ramps are generally designed to have suitable ramp slopes under typical deployment conditions, the slope of a deployed ramp can be adversely affected by operating conditions such as road crown, the availability of a “kneeling” capability in the vehicle, and the ramp being deployed to the road rather than a curb.
While it is possible to measure the deployment angle of the ramp relative to the ramp assembly's stowed position, i.e., relative to the floor of the vehicle, such a measurement does not account for the tilt of the bus due to road crown and/or a kneeling feature, both of which can add to the overall angle of the deployed ramp. Instead, the “absolute” ramp angle, that is the angle of the ramp relative to a horizontal plane rather than to the floor of the vehicle, is a better indicator of the potential difficulty a wheelchair-bound passenger may experience entering or exiting the vehicle. Thus, there is a need for a fold out ramp for a vehicle that provides an indication of the “absolute” angle of a deployed ramp relative to a horizontal plane.